Frosting Color Bleeding Into Cake

Problem #1- Hot pink frosting for pink zebra cake , in buttercream- bled into cake when. Had to add a decent amount of dark pink gel to get the color, with fear that this could happen or pink tongues. Not sure if it was smeared into cake with slicing or bled, but I assume bled.

#2- I had similar issue with my preserves filling, so I started putting a thin layer of BC underneath it with each layer. Solved the problem until the BC was hot pink :)

#3- I always so a light brushing of flavored simple syrup on my cakes, which really makes them fabulous tasting and moist. Could this be an issue causing the bleeding? These have been with the WASC ( 18.5 oz box) and I don't recall if it has happened with another recipe or not.

Would love some advice as the cakes do not look very attractive on the inside when sliced.

I don't know how you'd prevent the icing being smeared when cut, but if it is soaking into the cake, you could always try a (very) thin coating of white chocolate (or whichever kind suits your cake colour best) between the cake and the icing filling - both below and above. Obviously this would give a slight taste of chocolate to the cake...

Personally I would never agree to do this color in buttercream. I steer my customers wanting dark color icing away from buttercream and into fondant. Adding all the coloring into buttercream tastes TERRIBLE, IMHO.